The present invention relates to door latches, and more particularly relates to automatic door latches such as dead bolt locks.
Dead bolt locks are often used to secure doors. A typical dead bolt lock includes a bolt which extends from the door into an opening in a strike plate mounted in the door frame. In manual locks, the dead bolt is extended and retracted by a key from outside of the door, or by a key or handle from inside of the door. Although manual dead bolt locks provide increased security, they are inconvenient because a key must be used to lock the dead bolt after an individual has exited the door, or a key or handle must be used to lock the dead bolt from inside of the door. As a result, manual dead bolts are not always consistently locked.
Several types of dead bolt locks have been proposed in which the dead bolt is automatically locked when the door is closed. Examples of such automatic dead bolt locks are disclosed in U.S. Pat. Nos. 4,561,684, 4,671,549, 4,890,870, 4,945,737, 5,044,182, 5,516,160 and 5,615,919. Each of these patents is incorporated herein by reference.
Although conventional automatic dead bolt locks can provide increased usage in comparison with manual locks, they tend to be complex and require a large number of component parts. The requirement of many component parts adds to the cost of conventional locks, and also makes the locks susceptible to damage or failure during installation and use. In particular, conventional locks having components mounted on the exterior of the lock housing may be easily damaged during installation. Furthermore, some types of conventional automatic dead bolt locks require a mortise assembly for mounting on a door. In addition, conventional automatic dead bolt locks often are not compatible with standard predrilled door cut-outs. Another disadvantage of existing automatic dead bolt lock designs is that they often require the use of separate triggers or sensing pins. Such triggers and sensing pins typically require modifications to the door such as additional borings, or require the use of a hollow dead bolt to accommodate the components.
The present invention has been developed in view of the foregoing, and to address other deficiencies of the prior art.
An aspect of the present invention is to provide an automatic door latch. The latch includes: a housing; a latch retractably mounted in the housing and movable to an extended position, a partially retracted position and a fully retracted position; a spring biasing the latch toward the extended position; an actuator for moving the latch to the fully retracted position; a contact member mounted on the latch; and a multi-position switch mounted on the housing in releasable contact with the contact member. The multi-position switch allows the latch to move to the extended position when the multi-position switch is in a first or intermediate position, and holds the latch in the partially retracted position when the multi-position switch is in a second or extended position. The latch is preferably a dead bolt lock.
Another aspect of the present invention is to provide an automatic door latch including components mounted inside the housing of the latch. The components hold the latch in a partially retracted trigger position when the door is open, and allow the latch to move to an extended locking position when the door is closed.
A further aspect of the present invention is to provide an automatic door latch restraint assembly which manually secures the latch in a fully retracted unlocked position when automatic locking of the latch is not desired.
These and other aspects of the present invention will become more apparent from the following description.